1. Field of the Invention
The present invention relates generally to methods of correcting solder bumps, and more particularly, to an improved method of correcting solder bumps, which permits better soldering.
2. Description of the Background Art
Recent mobile instruments more often employ ICs having a Chip Scale Package (CSP) in the closest possible size to the outer shape of an IC (Integrated Circuit) chip or ICs of a Ball Grid Array (BGA) type. These types of ICs will be probably more often used for their applicability to compact, light-weight and thin electronics. When these kinds of ICs are actually mounted on a printed circuit board, solder bumps provided at a part of an IC are abutted against the printed circuit board at prescribed positions for reflow of the solder bumps. The IC and the printed circuit board are thus soldered.
FIGS. 7A and 7B show how a CSP type IC is soldered to a printed circuit board.
FIG. 7A is a cross section of the CSP type IC before reflow. An IC substrate 1 is provided with solder bumps 2. FIG. 7B shows the state after solder bumps 2 are abutted against printed circuit board 3 and reflowed. Solder bumps 2 are virtually fixed to printed circuit board 3 by the adhesive force of flux applied on the conductor portion of printed circuit board 3. Heat during the reflow allows solder bumps 2 to melt, and IC substrate 1 and printed circuit board 3 are joined accordingly.
In order to perform good soldering, a number of solder bumps 2 must be in contact with printed circuit board 3 at a time. In order to solder a number of solder bumps 2 to printed circuit board 3, variation in the height of solder bumps 2 should be generally 50 .mu.m or lower.